70 ANATOMY AND PHYSIOLOGY 



so-called ligament of the patella. Its location while the body is 

 erect is in front of the condyles of the femur, but in the sitting 

 position it is in front of the lower ends of the condyles, and in 

 kneeling it is beneath them. 



ARTICULATIONS OF THE LOWER EXTREMITY 



Hip- joint (ball-and-socket joint) (Enarthrosis) . Articular sur- 

 faces: head of the femur, and the acetabulum deepened by the 

 glenoid rim of the acetabulum (a rim of nbro-cartilage) . The 

 bones are directly connected by the ligamentum teres (or round 

 ligament) within the joint, which is attached by one extremity near 

 the middle of the head, and by the other to the bottom of the 

 acetabulum (Fig. 65). 



A capsule encloses the joint. It is strengthened by special 

 bands of fibers extending to surrounding bones one, the ilio- 

 femoral from the ilium to the great trochanter, resembles an in- 

 verted letter Y, and was formerly called the Y-ligament (also the 

 ligament of Bigelow) . The synovial membrane not only lines the 

 capsule but invests the ligamentum teres. 



Motions. Free motion in every direction, like that of the 

 shoulder. 



Knee-joint (hinge or ginglymus joint) (Fig. 66). Articular 

 surfaces: the condyles of the femur, the head of the tibia, and the 

 posterior surface of the patella. The two surfaces on the top of 

 the tibia are shallow, but their depth is increased by semilunar 

 fibro-cartilages attached around the borders, thus forming shallow 

 cups for the condyles. 



The femur and tibia are directly connected by two ligaments 

 within the joint, which cross each other and are therefore called 

 the crucial ligaments. (One passes from the' front of the spine to 

 the lateral condyle, the other passes from behind the spine to the 

 medial condyle.) The patella lies in front of the condyles, being 

 imbedded in a thick tendinous band about three inches long which 

 continues to the tuberosity of the tibia. (This band is really the 

 tendon of insertion for some thigh muscles, and is improperly 

 called the ligament of the patella.} It serves as the anterior liga- 

 ment of the joint but is at the same time the quadriceps extensor 

 tendon, sometimes called the patellar tendon. There are distinct 



